When a mobile unit is traveling, it may need to be handed off from one network to another. There are different types of wireless communication systems, such as general packet radio service (GPRS), global system for mobile (GSM)/enhanced data rates for GSM evolution (EDGE) radio access network (GERAN), and long term evolution (LTE) evolved universal terrestrial radio access network (EUTRAN). LTE/EUTRAN system has a different physical layer and a different architecture from those systems preceding it, i.e., GPRS, GERAN, or UTRAN. Since not all networks are identical, a method for supporting the handoff between systems would be beneficial.
United States Patent Publication Nos. US 2008/0268846A1 and 2008/0192697A1 describe a prior art method and system for supporting a handoff of user equipment from a GPRS/GERAN system to an LTE EUTRAN system, and vice versa, respectively. These references include a FIG. 1 exemplary diagram of a system including an LTE system architecture shown by an LTE/EUTRAN and its evolved packet core interworking with an existing GERAN, UTRAN, and their GPRS Core. The LTE/EUTRAN comprises an E-Node B that is connected (S1) to an evolved packet core containing a mobility management entity/user plane entity (MME/UPE) and an inter AS anchor Gateway. The Evolved Packet Core connects (S6) to a home subscriber service (HSS), and connects (S7) to a Policy and Charging Rules (PCRF). The inter AS Anchor gateway connects (Gi) to Operator IP Servers (such as IMS, PSS), connects (S2) to a Non-3GPP IP Access network 108, and connects (S2) to a WLAN 3GPP IP Access network 109.
The GPRS Core shown in FIG. 1 of these prior art references comprises a Serving GPRS Support Node (SGSN) which is responsible for Mobility Management, Access Procedures, and User Plane Control. The GPRS Core also comprises a Gateway GPRS Support Node (GGSN), where the network is connected to external networks and other operator servers. The Non-3GPP IP access network 108 includes connections to other technologies that are developed in other standard Forums such as 3GPP2 (CDMA2000) and WiMAX (IEEE 802.16 system). The WLAN 3GPP IP access network has WLANs incorporated into 3GPP systems via interworking architecture defined in 3GPP. These identified patent references, however, do not address the optimized handover procedures and system for an idle mode handover of user equipment from a 3GPP (EUTRAN) to a non-3GPP (HRPD cdma2000) system where the user equipment wishes to maintain connectivity with multiple PDN networks.
The Technical Specification 3GPP TS 23.402 V8.1.1 (2008-03) describes a 3rd Generation Partnership Project (3GPP) Technical Specification for enhancements and interactions with non-3GPP accesses. The particular version of the Technical Specification is Release 8, which describes the general network resources, entities, functions, and handover procedures for certain inter-technology combination handover systems, protocols, and procedures. Like the above-identified references, this Technical Specification also fails to address the optimized handover procedures and system for an idle mode handoff of user equipment from a 3GPP (EUTRAN) to a non-3GPP system (HRPD cdma 2000) where the user equipment wishes to maintain connectivity with multiple PDN networks. It would be beneficial to have a method and system that could support such an idle mode handover while maintaining the user equipment's connectivity to multiple PDN networks.